Field of Invention
The present invention relates to the technical field of a partial discharge test for electrical equipments, and more particularly to a testing device for propagation characteristic of electromagnetic wave in a gas insulated switchgear (GIS) and a testing method therefor.
Description of Related Arts
Due to the small occupation space and the good insulation performance, the GIS (Gas Insulated Switchgear) is widely applied in the power system. However, since the GIS has an enclosed structure, once an accident occurs, the consequences are much more serious than the open and separated type equipment, and the restoration of the fault of the GIS is extremely complex.
Partial discharge is generally regarded as a precursor of an insulation failure. The appearance of partial discharge indicates that there is a drawback in the installation, manufacture or even design of the GIS. The continuous partial discharge inside the GIS easily causes insulation breakdown accidents, so that blackout occurs, which brings enormous expense to national economy. Thus, charging the partial discharge of the GIS is very important. Therefore, testing the partial discharge is significant to the early detection and treatment of the GIS insulation failure.
Currently, the partial discharge ultrahigh frequency testing method is widely applied in the live detection of GIS partial discharge and plays a pivotal role in ensuring the safety of the equipment and detecting the defects thereof. While transmitting in the GIS, the partial discharge ultrahigh frequency electromagnetic wave signal generates attenuation. Mastering the attenuation characteristic of the ultrahigh frequency electromagnetic wave signal in the GIS is an important basis for analyzing and detecting on the field. Because the ultrahigh frequency electromagnetic wave signal has various phenomena in propagation, such as mode conversion. The conventional research on the propagation characteristics of the ultrahigh frequency electromagnetic wave signal mainly adopts a simulation method, and a finite-difference time-domain (FDTD) method is adopted for calculating, so as to obtain the propagation characteristic thereof. In fact, various materials are adopted by different manufactures for producing the disc insulators in GIS, and the sizes of the disc insulators are different under the identical voltage level, thus the simulation calculation is not capable of covering all types of the disc insulators. Thus, testing the propagation characteristics of the partial discharge electromagnetic wave signal of the GIS by an experiment in the laboratory to master the impact of the disc insulators on the propagation characteristic is a basis for accurately detecting on the field.